Nerve stimulation can be applied in the treatment of a range of conditions. Nerve stimulation may be applied to control muscle activity or to generate sensory signals. Nerves may be stimulated by surgically implanting electrodes in or near the nerves and driving the electrodes from an implanted or external source of electricity.
The phrenic nerves normally carry signals that cause the contractions of the diaphragm that are necessary for breathing. Various conditions can prevent appropriate signals from being delivered to the phrenic nerves. These include:                chronic or acute injury to the spinal cord or brain stem;        Amyotrophic Lateral Sclerosis (ALS);        disease affecting the spinal cord or brain stem; and,        decreased day or night ventilatory drive (e.g. central sleep apnea, Ondine's curse).These conditions affect a significant number of people.        
Mechanical ventilation (MV) may be used to help patients breathe. Some patients require chronic mechanical ventilation and many more patients require temporary mechanical ventilation. Mechanical ventilation can be lifesaving but has a range of significant problems and/or side effects. Mechanical ventilation:                tends to provide insufficient venting of the lungs. This can lead to accumulation of fluid in the lungs and susceptibility to infection and pneumonia.        requires apparatus that is not readily portable.        can adversely affect venous return because the lungs are positively pressurized.        interferes with eating and speaking.        requires costly maintenance and disposables.        tends to cause positive pressure ventilator induced lung injury (VILI) and ventilator associated pneumonia (VAP).        
A patient on mechanical ventilation is tied to a ventilator, and does not breathe independently. This can lead to atrophy of the diaphragm muscle (ventilator induced diaphragmatic dysfunction; VIDD) and an overall decline in well being. Muscle atrophy can occur surprisingly rapidly and can be a serious problem. In patients on mechanical ventilation, the central respiratory drive of the diaphragm is suppressed. The inactivity of the diaphragm muscle causes rapid disuse atrophy. According to a published study (Levine et al., New England Journal of Medicine, 358: 1327-1335, 2008), the diaphragm muscle could shrink by 52-57% after just 18-69 hours of mechanical ventilation and sedation. Ventilator-induced diaphragm atrophy could cause a patient to become ventilator-dependent. Patients in intensive care units (ICU) who become dependent on mechanical ventilation (MV) are at high risk of complications such as ventilator-acquired pneumonia (VAP) and nosocomial infections and are seven times more likely to die in the ICU. It has been reported that in 2008, 1.58 million ICU patients in the United States require MV every year, of which 20-30% (about 400,000 mechanically ventilated patients) have difficulty weaning from MV and are at risk of becoming ventilator-dependent.
Three methods have been used to reverse or slow down atrophy in disused diaphragm muscles by stimulating the phrenic nerves and are discussed below.
Method 1. Phrenic nerve pacing uses electrodes implanted in the chest to directly stimulate the phrenic nerves. The Mark IV Breathing Pacemaker System available from Avery Biomedical Devices, Inc. of Commack, N.Y., USA, is a diaphragmatic or phrenic nerve stimulator that has surgically implanted receivers and electrodes mated to an external transmitter by antennas worn over the implanted receivers. Implanting electrodes and other implantable components for phrenic nerve pacing requires significant surgery. The surgery is risky and complicated by the fact that phrenic nerves are thin (approximately 2 mm in diameter) and delicate. The surgery involves significant cost.
Method 2. Laproscopic diaphragm pacing developed by biomedical engineers and physician researchers at Case Western Reserve University is another technique for controlling breathing. Laproscopic diaphragm pacing involves placing electrodes at motor points of the diaphragm.
Method 3. A method using intravascularly implanted electrodes to stimulate a nerve has been developed by Joaquin Andres Hoffer and is described in U.S. patent application Ser. No. 12/524,571 (published on Feb. 11, 2010 as US2010/00336451) entitled “Transvascular Nerve Stimulation Apparatus And Methods”, which is hereby incorporated by reference.
Method 3 has advantages over Methods 1 and 2, because it does not require invasive surgery that would typically be performed under full anaesthesia. Furthermore, ICU patients are not typically eligible for Methods 1 and 2.
There remains a need for cost-effective, practical, surgically simple and minimally invasive apparatus and methods for nerve stimulation. There is also a need for apparatus and methods for facilitating patients on MV to breathe more naturally and to be weaned from MV. There is also a need for cost effective, practical apparatus and methods for installing and/or removing nerve stimulation apparatus.